Digesting apparatus



May 22, 1962 E. scHlNN DIGESTING APPARATUS Filed Jan. 28, 1959 INVENTQR. Ern sc Schmn 5f ,dwf SLW Aornegs 3,35h2 Patented May 22, 1962 3,035,962 D1GESTING APPARATUS Ernst Sebina, Weingartsbof, near Ravensburg, Win-temberg, Germany, assignor to Escher Wyss G.m.b.H.,

Ravensburg, Wurttemherg, Germany, a corporation of Germany Filed Jan. 28, 1959, Ser. No. 789,600 Claims priority, application Germany Feb. 6, 1958 Claims. (Cl. 162-17) This invention relates to an apparatus for continuously digesting brous vegetable materials, for example wood chips, which comprises a vertically mounted elongated vessel, in which the materials form a downwardly moving column, the said materials being introduced into the top of the pressure vessel, heated and digested by a supply of steam and, after the completion of the pulping, delivered from the bottom of the pressure vessel.

An apparatus of this type is known, in which the heating steam is fed to those parts of the materials which are situated in the lower part of the column of material in the pressure vessel.

The invention has for its object to ensure a better heating, a more intensive digestion and `a lower consumption of steam than in the known construction. In accordance with the invention, in an arrangemet of the above-described type, the steam is for this purpose fed to the upper part of the colum of material, means being thereby provided for distributing the steam within the material.

ln this way, a rapid and uniform heating of the introduced impregnated material can be effected. The steam in the space above the column of material is substantially at fresh steam pressure Iand thus forces the column of material toward the delivery end of the vessel, so that no mechanical means are required for the conveyance of the material. The column of material is in addition compressed, its compactness increasing with the increasing degree of pulping towards the delivery end. The compact lower power part of the column separates the steam space of the vessel and that part of the column which carries the free steam from the delivery chamber, so that substantially no steam escapes during the delivery. There is merely formed by the pressure difference between the pressure vessel and the delivery duct expansion steam which can be used for conveying the delivered materials.

A constructional example of the subject of the invention is illustrated in simplified vform in the drawing, which shows a vertical section through a pressure vessel and a container for receiving the materials delivered therefrom.

The illustrated arrangement comprises a pressure vessel 1, a feed hopper 2 and a rotary valve 3 driven by a motor 31. A jacket 4 formed with holes 41 and a pipe 5 formed with holes 51, together with feed pipes 6, serve for the supply of the steam. A delivery deviceV 7 driven by a motor 71 and an exhausting valve 8 are provided at the bottom of the vessel 1. An exhaust duct 9 leads into lan expansion container 10. In the pressure vessel 1, a column of material 11 is maintained at :a constant level by means of a feeler member 12 controlling the exhausting valve 8, whereby the digested material is continuously discharged from the bottom of the vessel 1. Situated above the column of material 11 is la steam space 13.

The material previously impregnated with the chemicals necessary lfor the digestion is introduced in portions without surrounding liquor into the pressure vessel 1 through the hopper 2 by way of the rotary valve 3. The material supply is quasi-continuous. The introduced material falls through the steam space 13, in which it is preheated, on to the column of material 11. ln the uppermost part of the column of material 11, the material is further heated and above all uniformly permeated with the steam, which is supplied through the pipes 6. The material is thus brought to digesting temperature already on the upper part of the material column. The steam may be supplied with a temperature of about C. and a pressure of Iabout 8 to 10 kg./cm.2 tabs. m-ay be maintained Within the vessel.

Means are here provided for the uniform distribution of the steam throughout the entire cross-section of the column of material. The pressure vessel is constructed with a double jacket. The lwall 1 of the Vessel forms the outer jacket, and the jacket 4 is the inner jacket. The inner jacket 4 comprises a sieve-like portion in the region of the uppermost part of the material column. The steam introduced through the pipes 6 is uniformly distributed in the intermediate space of the double jacket 1, 4 and -then passes through the holes 41 into the column of material 11. The holes 41 are distributed over the circumference of the jacket 4.

In order that the column of material 11 may at the same time also receive steam from the inside, the pipe 5 extending from above the material column 11 in the vertical direction through the uppermost part of the column 11 is provided, which is formed with lateral holes 51 for distributing the steam Within the column. Instead of a single pipe 5 two or more pipes may be provided for the supply of steam to the interior of the -material column 11.

The pipe 5 extends in the direction of movement of the compact column off material 11 where it comes into contact with the latter, and extends transversely to the direction of movement of the materialy only in the steam space 13, where the material is still loose.

The jacket 4 of the pressure vessel 1, which surrounds the column of material 11, widens conically in the downward direction, in order that the column of material 11 may pass through the vessel 1 with minimum resistance.

In the illustrated constructional example, the pressure vessel has a double jacket throughout, but it could -alternatively be only partially double-jacketed, preferably in its upper part.

What is claimed is:

1. Apparatus for continuously digesting fibrous vegetable materials comprising in combination a vertically mounted elongated pressure vessel; means at the top of said vessel for continuously introducing iibrous vegetable materials impregnated with digesting liquor into said pressure vessel; means for continuously discharging digested material from the bottom of said pressure vessel; means, responsive to the level of the column of material in said vessel, controlling the rate of discharge through said discharge means so as to maintain a constant level of said column of material intermediate the upper and lower ends of said pressure vessel; and means tor introducing steam into the space in said vessel above said level by distributedly introducing steam through the uppermost part of said column of material.

2. The combination deiined in claim 1 in which said last-mentioned means comprises a jacket encircling at least a portion of the side Walls of said pressure vessel below the level of material therein, said portion of the side walls being provided with a circumferential series of apertures; aand conduit means extending into said pressure vessel and including a perforated portion in the region of the uppermost part of said column of material.

3. The combination dened in claim v2 in which said 'conduit means comprises at least one pipe extending from above the column of material in a vertical direction through the uppermost part of Ithe material column, said pipe being provided with lateral holes yfor introducing steam distributedly through the uppermost part of said column.

4. The method of digesting fibrous vegetable materials in a vertically mounted pressure vessel, Which method consists in continuously feeding said materials, impregnated with digesting liquor, into the upper end of said vessel; removing the digested material from the lower end of said vessel; automatically controlling the rate of removal inresponse to the level of the column of 4the ibrous material in said vessel so as to maintain a constant level of material therein intermediate its upper and lower ends, thereby forming a space in said vessel above the level of said column of material and through which said materials fed to the vessel fall; and introducing steam into said space in said vessel by distributedly introducing said steam through the uppermost part of said column.

References Cited in the le of this patent UNITED STATES PATENTS Ball Feb. 16, Hildebrandt May 5, Brubacher July 16, Campbell Aug, 17, Natwick Apr. 13, Richter Nov. 23, Becker Nov. 6, Obenshain Apr. 16, Durant Oct. 28, Schandroch Mar. 3, 

4. THE METHOD OF DIGESTING FIBROUS VEGETABLE MATERIALS IN A VERTICALLY MOUNTED PRESSURE VESSEL, WHICH METHOD CONSISTS IN CONTINUOUSLY FEEDING SAID MATERIALS, IMPREGNATED WITH DIGESTING LIQUOR, INTO THE UPPER END OF SAID VESSEL; REMOVING THE DIGESTED MATERIAL FROM THE LOWER END OF SAID VESSEL; AUTOMATICALLY CONTROLLING THE RATE OF REMOVAL IN RESPONSE TO THE LEVEL OF THE COLUMN OF THE FIBROUS MATERIAL IN SAID VESSEL SO AS TO MAINTAIN A CONSTANT LEVE OF MATERIAL THEREIN INTERMEDIATE ITS UPPER AND LOWER ENDS, THEREBY FORMING A SPACE IN SAID VESSEL ABOVE THE LEVEL OF SAID COLUMN OF MATERIAL AND THROUGH WHICH SAID MATERIALS FED TO THE VESSEL FALL; AND INTRODUCING STEAM INTO 